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Folic acid

Folic acid is a type of B vitamin that is normally found in foods such as dried beans, peas, lentils, oranges, whole-wheat products, liver, asparagus, beets, broccoli, brussels sprouts, and spinach.

What is folic acid used for?

Folic acid is a synthetic form of folate, one of the B vitamins. You can normally get enough folate naturally in your diet. However, folic acid supplements are needed in the following situations:

To treat and prevent folate deficiency anaemia.

This type of anaemia can occur as a result of poor nutrition, malabsorption syndromes such as coeliac disease, alcoholism, pregnancy, or taking certain antiepileptic medicines. Your doctor might also ask you to take folic acid supplements to prevent anaemia if you have a condition where the body breaks down red blood cells too quickly (haemolytic anaemias, eg sickle cell anaemia), or if you're having kidney dialysis.

As a dietary supplement for pregnant women and women planning a pregnancy.

Folic acid supplements help prevent neural tube birth defects such as spina bifida and other congenital malformations such as cleft lip or palate in the developing baby.

To help reduce side effects associated with taking methotrexate for severe arthritis, Crohn's disease or psoriasis.

How does folic acid work?

Folic acid is an essential ingredient for making the genetic material of cells (DNA), and so is vital for growth and development. Folic acid is particularly important for maintaining a healthy nervous system and in the formation of red blood cells, which carry oxygen around the body.

When there's a deficiency of folic acid this causes a drop in the numbers of red blood cells in the blood, since folic acid is essential for their production. A course of folic acid supplements corrects the deficiency and allows red blood cell production to increase.

In pregnancy, folic acid is essential for the development of the baby's spinal cord and nervous system. Since this is one of the first things to develop in the baby, it's important that women take a daily supplement of folic acid both while trying to conceive and during the first 12 weeks of the pregnancy. It's difficult to get enough folic acid to prevent neural tube defects just from your diet.

Can I take folic acid if I'm breastfeeding?

Yes this is fine - folic acid passes into breast milk but it won't have any harmful effects on a nursing infant.

Does folic acid have side effects?

Not really. On rare occasions some people find that it gives them an upset stomach.

If you take more than the recommended amount of folic acid by accident it shouldn't cause any problems, because it is a water-soluble vitamin so your body will just naturally excrete any it doesn't need.

If you regularly take more than 1g folic acid daily this could mask a vitamin B12 deficiency, so you shouldn't do this unless it's prescribed by your doctor.

What is the recommended dose of folic acid?

In pregnancy:

For most women, the recommended dose of folic acid for preventing neural tube defects is 400 micrograms daily. This should be started as soon as you start trying for a baby, or as soon as you know you are pregnant if the pregnancy is unplanned. Keep taking 400 micrograms folic acid every day for the first 12 weeks of your pregnancy.

Some women are at a higher risk of conceiving a child with a neural tube defect and will need to take a higher daily dose of folic acid. You fall into this higher risk group if:

you, your partner, or someone in you or your partner's family, have a neural tube defect such as spina bifida

you've previously had a pregnancy affected by a neural tube defect

you have coeliac disease (or other malabsorption state)

you are diabetic

you suffer from sickle-cell anaemia

you are taking certain antiepileptic medicines.

You should talk to your doctor if you are in one of these higher risk groups because it's advised that you take 5 milligrams of folic acid daily, starting when you start trying for a baby and continuing until the twelfth week of pregnancy. This higher dose must be prescribed by a doctor.

For folate deficiency anaemia:

The dose of folic acid that your doctor prescribes to treat anaemia depends on what is causing the anaemia and your age. You'll usually need to take folic acid every day for a few months until the anaemia is corrected. Always follow the instructions given by your doctor.

If you've been prescribed folic acid to prevent anaemia your doctor might ask you to take a dose once every day, or once every few days. Again this depends on your individual circumstances so always follow the instructions give by your doctor.

To reduce side effects of methotrexate:

Your doctor may prescribe you 5mg folic acid to be taken once a week, on a different day of the week to your methotrexate dose.

How do I take folic acid?

Folic acid comes as tablets or liquid.

Folic acid can be taken either with or without food.

If you forget to take a dose at your usual time take it as soon as you remember. If you don't remember until the following day don't worry, just leave out the missed dose and take your next dose as usual when it's due. Don't take a double dose to make up for a missed dose.

Can I take folic acid with other medicines?

Avoid taking antacid medicines for indigestion in the two hours either side of taking your folic acid, as it's possible these could stop the folic acid from being properly absorbed from your gut.

Check with your pharmacist before taking folic acid supplements alongside other vitamin or mineral supplements, because these may already contain some folic acid.

It's fine to take folic acid with other medicines you can buy without a prescription, for example painkillers or antihistamines, assuming these are appropriate for you - always ask your pharmacist.

If you're already taking any prescription medicines, you should check with your doctor or pharmacist before you start taking folic acid to make sure that the combination is safe.

Folic acid may reduce the amount of the antiepileptic medicines phenobarbital, fosphenytoin, phenytoin and primidone in the blood. If you take folic acid with one of these antiepileptic medicines your doctor may need to increase the dose of your antiepileptic medicine to make sure your seizures remain controlled.

Folic acid may increase the risk of side effects from the anti-cancer medicines capecitabine, fluorouracil, tegafur and raltitrexed. If you're having treatment for cancer it's important that you always check with your pharmacist or cancer specialist before taking any other medicines as well, including vitamins, herbal remedies and non-prescription medicines, because this is not always safe.

Sulfasalazine may reduce the absorption of folic acid from the gut. Ask your doctor or pharmacist for advice if you're taking both.